1. Field of the Invention
The present invention relates to an improvement in the construction of ballasts for gas discharge lamps. More particularly, the present invention pertains to a socket, or sockets, for a gas discharge tube which contains the lamp driver portion of the system.
2. Background of the Invention
The lamp driver portion of an electronic ballast includes an oscillator, power semiconductors, and associated protection and filter circuits. Conventional systems arrange the circuitry in several configurations. For example, in copending patent application Ser. No. 08/496,623 for a gas discharge lamp and power distribution system filed Jun. 29, 1995, which depends from patent application Ser. No. 08/116,150 filed Sep. 2, 1993, incorporated herein by reference, both circuitry internal to the gas discharge tube and as a conformal extension of the tube are disclosed.
Other patents have differing circuitry arrangements. U.S. Pat. No. 5,294,865 to Haraden, for a lamp with integrated electronic module, has the ballast in the lamp base, which in turn screws into a conventional incandescent socket. U.S. Pat. No. 5,289,079 to Wittmann shows a compact fluorescent lamp and base combination, and U.S. Pat. No. 4,862,035 to Cunliffe et al teaches a fluorescent lamp unit having plural separate tubes and a particular arrangement of circuit elements. Both Wittmann and Cunliffe et al have starting circuitry in the compact fluorescent lamp base.
U.S. Pat. No. 5,086,249 to Blaisdell et al relates to a compact discharge lamp unit in which space is provided in the lamp base for a ballast. A ballast is attached to the side of the lamp base for a circular fluorescent lamp in a device according to U.S. Pat. No. 4,316,120 to Cotman et al, and U.S. Pat. No. 4,258,287 to Hetzel. In all of the foregoing arrangements, the lamp base screws into a socket, and when the lamp is replaced the ballast is replaced as well.
Since the average gas discharge lamp has a life expectancy significantly less than the life expectancy of the ballast, a ballast in perfectly good working order is discarded with the spent gas discharge lamp. Furthermore, the ballast adds significantly to the cost of the gas discharge lamp.